Consumer computing devices, such as desktop computers, detect the presence of a user based on user interactions (e.g. whether a user is typing on the keyboard or moving the mouse). The same techniques are used on mobile devices, such as smartphones, and may be used to control when to dim or turn off the display. Smartphones may also use a short-range sensor (i.e. one that operates over a distance of less than 15 cm) to detect when a user is holding the smartphone to their ear and this is used to deactivate the touch-screen.
The embodiments described below are not limited to implementations which solve any or all of the disadvantages of known methods of sensing user presence and location.